Related: interest, rent, usury

profit = price - cost

profit = 1/properly

Surplus is not Profit.  Profit occurs iff surplus is sold for price above cost.

Profit is the difference between the price consumer finally pays and the costs the owners already paid, plus any depreciation and so forth.

Profit measures the payer's dependence upon property owners.

Profit measures the payer's lack of properly.

Profit usually separates from wages when property has multiple owners because the owners that do not work there will not want to pay wages higher than market price.

But when property has few owners, they can collude to claim all incoming payments are wages.

For example, a solitary owner can hire as many workers as he likes and then just claim all profit as his own wage.
